If you are discussing the so-called locking trim pieces for the rear and/or front glass--AKA windshield and backlight--then--IF this applies to your question
1) the material you are describing is anodized aluminum--often mistakenly called chrome--it should not be sanded and if re-finishing is a must it is probably a project for a professional polisher
2) anodized coatings can be professionally polished to remove same and then left sans coating--that will require periodic polishing to maintain its shine--how often depends on weather factors, where you keep the car, etc
3) these parts are difficult to handle due to their shape and a professional polishing shop may or may not agree to polish out those pieces
4) the lower trim line that goes around the car is also anodized aluminum--and a local shop here in SoCal has done the polishing of same--then follows polish with application of a new clear coating material that appears superior to the original anodizing--one of our local E-9 owners--Chris in Huntington Beach has had this done and it appears as or better than new
the shop that does this is Speedway Metal Finishing in Santa Ana, CA--their wheel refinishing (for undamaged wheels) and polishing services are of factory quality--I have used their services for years--as have many local owners and restorers--IMO their prices are quite reasonable--
phone contact is--714-542-7778 not aware if they have a website.
HTH